Field of the Invention
The present disclosure relates to a spindle apparatus for a machine tool, and more specifically relates to an improvement of a cooling structure for cooling a periphery of a motor which rotatably drives a spindle.
Description of the Related Art
The following description of related art sets forth the inventors' knowledge of related art and certain problems therein and should not be construed as an admission of knowledge in the prior art.
A spindle apparatus of this kind is provided with a cooling structure for cooling a periphery of a motor to avoid adverse influences to processing precision due to heat generation of a motor which rotatably drives a spindle. For example, in Japanese Unexamined Patent Application Publication No. 11-48087 (Patent Document 1), a ventilation fan is provided in an upper opening of a headstock to suck air around a bed through an air inlet of the bed and discharge it upward through the upper opening by passing the air through a cooling space surrounding a stator via a lower opening of a headstock fixing section.
In the meantime, it is generally difficult to integrally form a headstock having a motor accommodation section and a cooling medium accumulation part so as to include cooling passages for cooling a motor. For this reason, in the cooling structure of Patent Document 1, the headstock fixing section having a lower opening and a headstock main body having a cooling space are produced separately and then assembled. This causes a problem that the production cost arises.
Further, in the conventional structure of Patent Document 1, air is sucked from an air suction opening of a bed and discharged upward from the upper opening by passing from the lower opening of the headstock fixing section through a cooling space surrounding the stator. In other words, a cooling fluid is merely moved upward from the lower section of the headstock. Therefore, the supply quantity of the cooling fluid tends to become uneven especially in the axial direction of the motor. This raises a concern that the periphery of the motor cannot be cooled evenly.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. For example, certain features of the preferred described embodiments of the invention may be capable of overcoming certain disadvantages and/or providing certain advantages, such as, e.g., disadvantages and/or advantages discussed herein, while retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.